#ifndef _TREE_HPP_
#define _TREE_HPP_
struct TreeNode{
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode(int x):val(x),left(nullptr),right(nullptr){}
    TreeNode() : val(0), left(nullptr), right(nullptr) {}
    TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
};
#endif
